The invention concerns a head for a prop of formwork for a concrete ceiling, having an end piece facing the concrete ceiling and of which the longitudinal axis extends perpendicular to the plane of the concrete formwork, and a prop of a concrete formwork, and a concrete formwork with such a prop head. The prop head in accordance with the invention is in particular suitable for use in formwork for slanted concrete ceilings, i.e. for concrete ceilings which have a vertical component of direction.
Formwork for concrete-cast ceilings (ceiling formwork) usually comprises a system of steel or wood girders, for example, onto which the formwork panels which shape the bottom side of the concrete ceiling are placed. This is referred to as grid formwork. Alternatively, the formwork panels may be fixed to a rigid substructure, mostly consisting of aluminum girders. Such a substructure, having at least one formwork panel fixed to it, is referred to as a panel. The ends of the girders and/or the panel are fixed to prop heads which extend the props of the concrete formwork axially towards the concrete ceiling. The girders of the concrete ceiling formwork have clasping mechanisms disposed at their ends by means of which they are often clasped by clasping structures (receivers) shaped to complement the clasping mechanisms in the region of the end piece end of the prop head facing the concrete ceiling, which allows swift mounting of the ceiling formwork. In ceiling formwork, the girders are always aligned perpendicular to the longitudinal axis of the prop head, since the clasping structures are configured in such a way that the girders are aligned perpendicular to the prop head. The girders of the concrete formwork can only absorb the vertical forces caused by the loads they support, since they can divert forces substantially only in their axial direction.
Prop heads which are configured as so-called drop-heads are known to also facilitate dismounting of such ceiling formwork. In such drop-heads, the clasping structures of the drop-head are configured on elements which move axially in the longitudinal direction of the prop and/or the drop-head, wherein the elements can be secured by means of wedges and/or wedge plates, for example, and which hold the completely mounted ceiling formwork ready for concrete-casting. Once the concrete ceiling has sufficiently hardened, the wedge and/or wedge plate, for example, can be knocked out and/or released, whereupon the mobile element can be shifted away from the concrete ceiling or falls down on its own by gravity. In this dismantled position, the girders can easily be dismounted. Such drop-heads and associated concrete formwork are disclosed, for example, in U.S. Pat. Nos. 3,915,423 and 3,239,188.
In case of slanted ceiling formwork, i.e. formwork for a slanted concrete ceiling, the girders of the concrete formwork and the formwork panels disposed on them do not extend exclusively horizontally. Nevertheless, the girders are disposed perpendicular to the longitudinal axis of the prop heads in known slanted ceiling formwork. The props are therefore placed upon a floor plate, for example, slanted relative to the vertical at an angle which tallies with the incline of the ceiling to be concrete-cast. As the downward forces produced by the ceiling formwork and the concrete ceiling would cause the girders of the ceiling formwork to collapse, these downward forces are captured by means of bracing means, for example chains, which are fixed to the floor and the ceiling formwork. The stability of the props is thus secured by a bracing system. This bracing system must be applied with precision to ensure the stability of the ceiling formwork. Furthermore, the bracing system considerably affects the accessibility of the room below the ceiling to be concrete-cast. Therefore, the effort required to concrete slanted ceilings is considerably higher than in merely horizontal ceilings.
DD 254 045 A1 discloses a prop head of the inventive kind. This prop head has a hinge mechanism disposed at the end facing away from the concrete ceiling via which it is connected with a prop. When used in formwork for a slanted concrete ceiling, the prop head is offset from the prop, i.e. mounted in a hinged position. In this embodiment, the end of the prop head facing the concrete ceiling is positioned at a slant angle next to the longitudinal axis of the prop, creating overturning torques which may render the concrete formwork unstable.
The invention is based on the task of providing a prop head, and a prop, and concrete formwork which avoid the disadvantages of prior art, wherein in particular the structure of formwork for slanted ceilings is rendered more simple.
This task is fulfilled by the prop head, and the prop, and the concrete formwork according to the independent claims. The dependent claims are preferred embodiments of the invention.